Re: [PATCH 7/8] vhost: use kernel_copy_process to check RLIMITs and inherit cgroups

[Hillf Danton <hdanton@sina.com>]

On Thu, 16 Sep 2021 16:20:50 -0500 Mike Christie wrote:
>  
>  static int vhost_worker_create(struct vhost_dev *dev)
>  {
> +	DECLARE_COMPLETION_ONSTACK(start_done);

Nit, cut it.

>  	struct vhost_worker *worker;
>  	struct task_struct *task;
> +	char buf[TASK_COMM_LEN];
>  	int ret;
>  
>  	worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
> @@ -603,27 +613,30 @@ static int vhost_worker_create(struct vhost_dev *dev)
>  		return -ENOMEM;
>  
>  	dev->worker = worker;
> -	worker->dev = dev;
>  	worker->kcov_handle = kcov_common_handle();
>  	init_llist_head(&worker->work_list);
>  
> -	task = kthread_create(vhost_worker, worker, "vhost-%d", current->pid);
> -	if (IS_ERR(task)) {
> -		ret = PTR_ERR(task);
> +	/*
> +	 * vhost used to use the kthread API which ignores all signals by
> +	 * default and the drivers expect this behavior. So we do not want to
> +	 * ineherit the parent's signal handlers and set our worker to ignore
> +	 * everything below.
> +	 */
> +	task = kernel_copy_process(vhost_worker, worker, NUMA_NO_NODE,
> +				   CLONE_FS|CLONE_CLEAR_SIGHAND, 0, 1);
> +	if (IS_ERR(task))
>  		goto free_worker;
> -	}
>  
>  	worker->task = task;
> -	wake_up_process(task); /* avoid contributing to loadavg */
>  
> -	ret = vhost_attach_cgroups(dev);
> -	if (ret)
> -		goto stop_worker;
> +	snprintf(buf, sizeof(buf), "vhost-%d", current->pid);
> +	set_task_comm(task, buf);
> +
> +	ignore_signals(task);
>  
> +	wake_up_new_task(task);
>  	return 0;
>  
> -stop_worker:
> -	kthread_stop(worker->task);
>  free_worker:
>  	kfree(worker);
>  	dev->worker = NULL;
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 102ce25e4e13..09748694cb66 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -25,11 +25,16 @@ struct vhost_work {
>  	unsigned long		flags;
>  };
>  
> +enum {
> +	VHOST_WORKER_FLAG_STOP,
> +};
> +
>  struct vhost_worker {
>  	struct task_struct	*task;
> +	struct completion	*exit_done;
>  	struct llist_head	work_list;
> -	struct vhost_dev	*dev;
>  	u64			kcov_handle;
> +	unsigned long		flags;
>  };
>  
>  /* Poll a file (eventfd or socket) */
> -- 
> 2.25.1
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